Method of producing laminated bottles having peelable inner layer

ABSTRACT

The present invention provides a method of making laminated bottles each having an outer layer and an inner layer capable of delaminating from the former layer. The method consists of the step of injection molding an outer preform from a molten first resin, and the next step of injection molding an inner preform inside the outer preform, using a molten second resin. The method further has the final step of blow molding a parison composed of the outer and inner preforms so as to form each laminated bottle. The second resin has a melting point lower than that of the first resin, nevertheless and contrarily to the prior art, precise parisons affording satisfactory lamination can now be prepared by the injection molding steps. In addition, ventilation holes are formed in the outer layer readily and surely without damaging the inner layer.

FIELD OF THE INVENTION

The present invention relates to a method of making laminated containerswhose peripheral walls are composed each of an outer layer and an innerlayer disposed therein to be delaminated therefrom. The inventionrelates also to a method of forming at least one hole solely in theouter layer constituting an injection-laminated parison or the like usedto blow mold a delaminatable container.

BACKGROUND OF THE INVENTION

Japanese Patent Laying-Open Gazette No. Hei. 4-267727 discloses alaminated container having a delaminatable layer designed such thatambient air is inhibited from entering the container through a mouthwhile allowing its content to be discharged. This container is composedof an impermeable inner layer and a squeezable outer layer, wherein theinner layer can be readily delaminated from the outer layer in which atleast one ventilation hole is formed such that the ambient air cancommunicate with the space between the layers. In this way, the innerlayer will spontaneously shrink as quantity of the content decreases,with the ambient air flowing into the space through said hole so thatonly the outer layer can restore its normal configuration. Its contentremains satisfactory in quality, from the beginning to end of use,without being impaired by air or light beams.

The direct blow molding known in the art may be an example of the methodof manufacturing laminated bottles of this kind. In this method, amulti-layer extruder is used to extrude an inner resin layer and anouter resin layer laminated thereon to form a cylindrical parison. Thisparison will be placed in a blow forming mold (and pinched off toprovide a closed bottom in a finished bottle), axially stretched andsimultaneously blow molded, to thereby give the finished bottle havingthe delaminatable inner layer.

In the described prior art laminated bottles, their inner layers shouldhave each a highly precise wall thickness. In particular, evenness inwall thickness is more strictly required for profiled or ‘modified crosssection’ bottles such as elliptic bottles. In order to meet such arequirement, the so-called ‘injection blow-molding’ method is preferablewherein a laminated parison that has been prepared by injection moldingwill be blow molded.

In many cases, the described laminated bottles are used as containersfor holding therein certain liquids (such as hair-dye) that are likelyto change in their properties due to contact with air. Selection of aresin material for forming the inner layer must be done carefully lestthe content should undergo any noticeable deterioration even if storedfor a long time. Further, the material is to be selected from relativelysoft ones because the inner layers have to gradually shrink during use.Examples of materials satisfying these conditions may be polyolefinresins such as a polypropylene and a polyethylene. Polyolefin resins arehighly resistant to chemicals and almost impermeable for gases. Certainmedically active ingredients prone to deteriorate due to expiration ofwater vapor are protected from deterioration. A ‘PET’ or the like resinmay be preferred as a material for forming the outer layer.

Polyolefin such as polyethylene have lower melting points than saturatedpolyesters such as PET. If the injection-stretching method accompaniedby the subsequent blow-molding step is applied to preparation of alaminated parison wherein an inner preform is injected prior toinjection of an outer preform, then the following problem would occur.Since the thermal deformation temperature of the already prepared innerpreform is lower than the molding temperature for the outer preform, theinner preform will probably melt when molding the outer preform, failingto manufacture useful multi-layer preforms.

Since the inner layer of said laminated container will gradually shrinkas its content is consumed, it is desirable that the outer and innerlayers firmly engage with each other at bottom in order to smoothen theshrinkage of inner layer. It is described in the above Gazette that theouter and inner layers are fixed on each other at their bottoms, but notteaching how to do this. On the other hand, Japanese Utility ModelPublication No. Hei. 7-48519 shows a pinched-off ridge that is formed inthe container bottom so as to unite the outer layer with the innerlayer. In detail, when blow molding the container, a raw multi-layerpreform that has been extruded from a molding apparatus through a nozzlethereof will be pinched off in such a manner that mutually-engagingcorrugations are formed by pressing bottom portions of the layerssideways. This structure will provide the outer and inner layers firmlybonded to each other, though an extra additional device is necessary topress the bottom portion, failing to match theinjection-stretching-blow-molding method.

A first object of the present invention is therefore to provide a methodof making a laminated bottle by injection molding a laminated parisonthat will subsequently be blow molded smoothly to form the bottle of animproved quality, wherein optimum materials are chosen for an innerlayer and an outer layer, respectively. Another object is to facilitatethe inner layer to be easily combined in part with the outer layer.

A user may close with his or her finger(s) a ventilation hole(s) thatis(are) formed in the prior art delaminatable container for introducingambient air in between its layers. Alternatively, a film tag may beadhered in part to the rim of the ventilation hole so that the taglarger than the hole is disposed inside the outer layer. Such a kind ofvalve will allow the air to flow inwards through the outer layer, butnot through the inner layer. With the container being gripped by theuser, the ventilation hole will be closed with his or her fingers or bythe valve so as not to allow any amount of air to leak out from theinterlayer space. Such a depressed outer layer will cause the interlayerair to press in a centripetal direction the inner layer to exude thecontent out of the container.

In the prior art of this type, whether accompanied by the valve or not,the outer layer having the ventilation hole(s) has generally been blowmolded or hot molded before integrating the inner and outer layers oneanother. Alternatively, a protrusion jutting from the inner walldefining a blow-molding cavity has served to directly form a ventilationhole or to form a groove readily transformable into a hole.

The prior art method consisting of the steps of preliminarily blowmolding the outer layer and subsequently integrating it with the innerlayer does however require so many steps as raising manufacture cost ofthe delaminatable containers and lowering yield thereof. The lugprotruding inwardly from the inner wall defining the blow-molding cavityis described as a means useful to form the ventilation hole solely inthe outer layer. However, there is a possibility that such a lug wouldinjure the inner layer. The forming of such a preliminary groove in theouter layer may be possible, but semi-finished containers have to beafter-treated one by one with hand to transform them into the holes.Operation efficiency in manufacture of those containers will thus belowered, raising manufacture cost. Also disadvantageously, the lateopening of the hole in the outer layer is likely to damage the innerlayer.

A second object of the present invention is to provide a method ofmaking a laminated bottle in such a manner that at least one ventilationhole can be formed easily and surely in an outer layer, without any fearof injuring an inner layer, and more particularly to provide a method offorming at least one hole only in the outer layer of an injection moldedlaminated article such as a parison for use to blow mold a laminatedcontainer having the delaminatable inner layer.

DISCLOSURE OF THE INVENTION

The present invention provides a method of making a laminated bottlehaving a outer layer and a inner layer laminated on an inner surface ofthe outer layer so as to be capable of delaminating from the surface.The present method may comprise the steps of injection molding a preformfor the outer layer by injecting a molten first resin, then injectionmolding inside the preform a further preform for the inner layer byinjecting a molten second resin so that the preforms comprise a parison,and finally blow molding the laminated bottle by blowing the parison. Inthis method, the second resin may have a melting point lower than thatof the first resin.

In the method of the present invention, a injection mold may be used forsaid injection molding of the inner preform, the mold comprising a coresegment and a cavity segment, the core segment having an injection gateformed therein. Furthermore, injection molding the inner preform maycomprise the steps of loading the outer preform in the cavity segment,subsequently clamping the core segment and the cavity segment, andfinally injecting the second resin inside the outer preform through thegate in the core segment.

Also in the method of the present invention, the method may furthercomprise the step of forming a through-hole in the outer preform beinginjection molded. The through-hole may preferably be formed at a portionthereof facing an injection gate for injecting the second resin.

It may be possible that injection molding the inner preform comprisesinjecting the second resin through the gate and also the through-hole toflow along an inner surface of the outer preform.

Further in the method of the present invention, the through-hole may beformed by a first pin, the pin projecting toward a further injectiongate for injecting the first resin through it after injecting of thefirst resin has been finished so that an end portion of the pin strikesthe further gate.

Further in the method of the present invention, a flange may be formedof the second resin when injection molding the inner preform, such thatthe flange formed integral with the inner preform is located outside thethrough-hole formed in the outer layer.

In the method of the present invention, the inner preform may beinjection molded so as to a bulge of the second resin is formed, thebulge projecting through the through-hole from the outer preform.Furthermore, a stretching rod used for longitudinal stretching theparison may depress and collapse the bulge at said blow molding.

In the method of the present invention, the inner preform may beinjection molded to be integral with a plurality of thickened portionsextending vertically at angular intervals.

Also in the method of the present invention, the inner preform may beinjection molded to have a body that is formed integral with at leastone thickened portions extending in a helical direction.

The present invention is applicable to make the laminated bottle havingat least one ventilation hole to allow ambient air to flow in betweenthe outer and inner layers. In this case, such ventilation hole may beformed at the step of injection molding the outer preform, and when theinner preform is subsequently injection molded, a second pin may havebeen inserted from outside and through the outer preform in such amanner that an end portion of the second pin is held substantially inflush with the inner surface of the outer preform.

In the method of the present invention for manufacture of the laminatedbottle having the ventilation hole, a cavity segment and a first coresegment for molding the outer preform may be used for injection moldingthe outer preform. Preferably, this method further comprising theadditional step of replacing the first core segment with a second coresegment for molding the inner preform, without removing the outerpreform out of the cavity segment, with the additional step beinginterposed between the steps of injection molding the outer and innerpreforms. The cavity segment and the second segment may be used forinjection molding the inner preform. Furthermore, forming theventilation hole may comprise striking the second pin against the firstcore segment before the resin of the outer preform cures at the step ofinjection molding the outer preform. The ventilation hole preferableremain closed with the second pin during injection molding the innerlayer.

Additionally, the second pin may be capable of shifting between itsprojected position where the pin strikes the first core segment clampedto the cavity segment and its retracted position where the pin isembedded in the cavity segment.

Also in the method of the present invention, the outer preform may beheld by a lip mold all through the first, second and third steps. Inthis case, the second pin may be capable of shifting between itsprojected position where the pin strikes the first core segment clampedto the cavity segment and its retracted position where the pin isembedded in the lip mold. The pin at the projected position will clogthe ventilation hole but the pin at the retracted position leaves thehole opened.

Further in the method of the present invention, a first injection moldmay be used for injection molding the outer preform and a secondinjection mold is used for injection molding the inner preform. Further,this method preferable comprises the steps, between the steps ofrespectively injection molding the outer and inner preforms, ofreleasing the outer preform from the first mold, loading the releasedouter preform into the second mold, inserting the pin into theventilation hole that has been formed in the outer preform. The pin mayremain left is the ventilation hole during injection molding the innerlayer.

In the method of the present invention, the parison may be blow moldedsuch that the stretching for orientation of the preforms is conductedfor the portion thereof located below the ventilation hole.

Also this invention proposes a method of making at least one hole solelyin an outer layer of an injection molded laminated product having aninner layer formed on an inner surface of the outer layer, the methodcomprising:

the step of injection molding the outer layer, and the step ofsubsequently injection molding the inner layer using a resin whosemelting point is lower than that of a further resin forming the outerlayer,

wherein the at least one hole is formed during the step injectionmolding the outer layer,

and the inner layer is injection molded such that an inner end of atleast one pin inserted from outside is temporarily located substantiallyin flush with the inner surface of the outer layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of a comb shaped product comprising as a partthereof a laminated bottle that may be manufactured by a method whichthe present invention provides in an embodiment thereof;

FIG. 2 also is a side elevation of the laminated bottle included in thecomb shaped product shown in FIG. 1, from which a cap of the comb-likeshape is removed;

FIG. 3 is an enlarged cross section of a principal portion that isincluded in the comb shaped product shown in FIG. 1;

FIG. 4 is an enlarged elevation of a bottom of the bottle constitutingthe comb shaped product illustrated in FIG. 1 and shown partly In crosssection;

FIG. 5 is a scheme illustrating an injection step performed at aninjection station employed in an embodiment of the present invention (soas to mold a preform constituting an outer layer);

FIG. 6 also is a scheme illustrating another injection step performed atthe injection station (so as to mold a preform constituting an innerlayer);

FIG. 7 is a scheme of a blowing station where an integrated preform isbeing moved at the transfer step;

FIG. 8 is likewise a scheme of a clamping-and-stretching step carriedout at the blowing station;

FIG. 9 is a similar scheme of a blowing-and-cooling step also carriedout at the blowing station;

FIG. 10 is a scheme of an ejection step that is carried out at anejection station so as to take out a molded product;

FIG. 11 is a scheme of the step of fastening mold segments together atan injection station (before molding an outer preform) in anotherembodiment of the present invention;

FIG. 12 is a scheme illustrating an injection step performed at theinjection station (to mold the outer preform);

FIG. 13 also is a scheme illustrating another injection step performedat the injection station (to mold an inner preform);

FIG. 14 is a scheme of the transfer step of transferring an integratedpreform (viz., parison) at a blowing station,

FIG. 15 is likewise a scheme of the step of clamping and stretching theparison at the blowing station;

FIG. 16 is a similar scheme of the step of blowing and cooling thestretched parison at the blowing station;

FIG. 17 is a scheme of the step of ejecting a finished product at anejection station so as to take it out;

FIG. 18 is a plan view of an example of the parison used in the methodof making the laminated bottle according to the present invention;

FIG. 19 is a vertical cross section of the parison shown in FIG. 18;

FIG. 20 is a plan view of another example of the parison used in themethod of making the laminated bottle according to the presentinvention; and

FIG. 21 is a vertical cross section of the parison shown in FIG. 20.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a method of making laminated bottleswhose peripheral walls are composed each of an outer layer and an innerlayer disposed therein, a resin of which has a lower melting point thanthat of the outer layer. The method is characterized in that an innerpreform is molded inside the outer layer by injection molding the resinof the melting point lower than that of the outer preform that has beeninjection molded, so as to prepare a parison composed of the injectionmolded preforms. According the invention, this parison will then besubjected, as usual, to the blow-molding step to provide a finishedlaminated bottle. In this invention, the inner preform is molded afterthe outer preform has been molded. Therefore, even if the inner preformis made of a polyolefin or the like and the outer preform is made of a‘PET’, ‘EVOH’ or the like, these two kinds of resins will not intermixwith each other but be demarcated from each other. Consequently, thedelaminatable laminated bottle made by this method has the inner layerthat is readily exfoliated from the outer layer in use, with a liquidcontent in this bottle being protected well from change in itsproperties. Both the outer and inner layers of each bottle providedherein may respectively have bodies and mouths. The body of the outerlayer may be squeezable, or alternatively be rigid in case of mounting apump in a mouth of the bottle.

In the method of the present invention, the injection molding of theinner layer may be conducted using an injection mold that consists of acore segment having an injection gate and a cavity segment. Further, theinner preform may be injection molded in such a manner that the outerpreform is inserted at first in the cavity segment of the mold, the coreand this cavity segments are then fastened to each other. Finally, thesecond resin is injected through the injection gate onto an innersurface of the outer preform, in a case wherein the gate is formed inand through the core segment. This mode will not make any gate flashesexposed to the outside, but rather give products an improved appearance.Preferably, the gate may be formed in and through pointed central regionof the core segment.

A through-hole may be formed in the outer preform when this preform isinjection molded, so that a gate penetrating the cavity segment forinjection of the second resin does face the through-hole. In this case,a molten resin will be guided through this gate and the through-holeinto the interior of the outer layer that has been placed in the moldfor injection molding the inner layer.

Further, the through-hole in the outer preform may be produced byputting a pin towards the gate so as to bring a free end of the pin intocontact with the gate, after injection of the resin though the gate. Thegate in this case will be sealed up with the pin lest any gate flashesshould be produced, thus making it unnecessary to remove them.

A flange may be produced of the same resin as the inner preform so as tobe disposed outside the through-hole during the injection molding of theinner preform. The flange is integral with this portion disposed in thethrough-hole and integral with the inner preform. Such a flange isconsiderably larger than the through-hole in diameter so that the innerlayer can be secured to and fixed in the outer layer. Due to thisfeature, a stretching rod used at the step of stretching and blowmolding will be prevented from peeling the inner layer off the outerlayer. If such a flange is located at the bottom of the bottle, theinner layer will be delaminated from the outer layer during use,avoiding any curling up of the inner layer's lower end portion. The‘flange’ may be formed in flush with the outer surface of the outerlayer, or jutting outwards from the through-hole.

The method of the present invention is adapted for application tomanufacture of laminated bottles each having a delaminatable innerlayer. For this purpose, the method may comprise the steps of injectionmolding the outer preform and subsequently the inner preform so as toallow the blow molded inner layer to be delaminated from the outer layerin use. The method may also comprise the step of forming ventilationholes in the outer layer so that ambient air flows in between the outerand inner layers. In order to enable the inner layer to be delaminatedfrom the outer layer after blow molded and during use, wall thickness ofthe preform may be determined taking into account relevant parameterssuch as stretch ratio and physical properties of the materials. Theinner preform will be injection molded using a mold that ensures such awall thickness. By selecting a proper resin and wall thickness, the thusinjection-and-blow molded outer preform will be capable of squeezeitself.

In case of using the method to manufacture laminated bottles each havinga delaminatable inner layer, a resin of the inner preform may preferablybe projected out of the through-hole of the outer preform beforeinjection molding the inner preform. A stretching rod used to conductthe longitudinally stretching step will collapse the projection made ofthe resin forming the inner layer. The longitudinal stretch conducted atthe step of blow molding is effective to press a bottom of a parison andto reform it as a flange disposed outside the bottom of outer layer. Theinner and outer layers are thus fixedly secured to each other at thebottom. In this way, any additional step is not needed to integrate theinner and outer layers at their bottoms.

In addition, the injection molding of the inner preform may be conductedsuch that a plurality of thickened portions are formed integral with thepreform in such a manner that each portion extends longitudinally andcircumferentially. The blow molded laminated bottles will have each theinner layer that is formed integral with pillar- or rib-shaped thickenedportions. Each of those thickened portions shows such an improveddeformation resistance that the inner layer is not readily delaminatedfrom the outer layer. Flat regions each interposed between the linearthickened portions of the inner layer gradually will shrink inwardly soas to provide the inner layer with uniform shrinkage and deformationover full height of each bottle. Neither a middle portion of the innerlayer nor an upper end portion thereof (located close to a mouth of thebottle) will shrink sooner than the lower portion of the layer. Thus,the latter portion will be protected from being sealed not to exhaust aliquid content. Since the inner preform is injection molded herein, theforming of such thickened portions can be effected reliably to giveproducts each having a uniform internal texture.

It is also possible to provide the inner preform with a body-shaped partthat has a thickened region extending in a helical direction. Thisregion may be a helical protrusion formed integral with the innersurface of the body-shaped part. Alternatively, a helical recess may beformed in the inner surface of the outer preform, and then the innerlayer is injection molded inside the outer preform to produce thehelical thickened region.

Also, an injection mold used herein to produce an outer preform for thelaminated container may comprise a cavity segment with a closed bottomin combination with a core segment having a pin. This pin is intended tocontact an inner surface of the closed bottom of the cavity segment.Such a type of the mold may be suited to preparation of the outerpreform in the present invention. If this mold is used to form an outerlayer, then a space occupied by the pin cannot be filled with a resin ofthis preform. Thus a through-hole will be produced to extend from anouter surface to inner surface of the outer layers preform. In short,the hole is formed through the bottom of this preform while moldingsame.

Alternatively, then injection mold just described above to produce theouter preform for the laminated container may comprise the core segmentwith a closed bottom may be employed in combination with the cavitysegment having a pin to contact a closed end of the core segment.

Each of these injection molds may have the pin being capable ofprojecting into and being retracted from so that a gate facing the pinis clogged therewith.

The method of the invention described above may utilize the followingmanufacturing apparatus. This apparatus is composed of a device forinjection molding the outer layer, a further device for injectionmolding the inner layer, and a still further device for blow moldingthem. A cylindrical outer preform having a bottom and a through-holeformed through the bottom is injection molded by the first-mentioneddevice. The further device for injection molding the inner layer injectsan inner preform inside the outer preform. The still further device blowmolds a parison that is formed with a bottom and composed of the outerand inner preforms, while biaxially stretching the parisonlongitudinally and transversely in such a way that the inner layerdelaminatable from the outer layer is laminated on the inner surfacethereof to provide a laminated container. The device for injectionmolding the inner preform may have a gate for passing a molten resinthrough the hole to thereby inject it from outside into the outerpreform. The gate may be spaced outwards from the through-hole. Usingthese devices, the gate formed in a mold for injecting the inner layeris spaced a distance from the through-hole of the outer preform. Aportion of the resin for the inner preform protrudes out of the hole andsolidifies to be left there, when injection molding the inner preformwith the further device. At the step of longitudinally andcircumferentially blow molding the parison using the still furtherdevice, a stretching rod may collapse this protrusion when the parisonwith bottom is longitudinally stretched. Subsequently, the resin mayspread on the outer surface of the outer layer's bottom to integrate theouter and inner layers at the bottom of the container. It is possible toform the inner layer using such a resin as having a lower melting pointthan that of the outer layer. In other word, it is now possible tochoose the most preferable resin because the molten resin of the innerpreform is introduced through the hole already formed in the bottom ofthe outer preform, so as to flow on and along the inner surface thereof.

As described above, the present invention is characterized in that theinner preform having a lower thermal deformation temperature than themolding temperature of the outer preform is molded therein after moldingsame. In the prior art, wherein a preform of an inner layer has beenmolded at first, the inner preform has tended to thermally deform itselfwhen subsequently molding the outer preform. This drawback is overcomeherein, and satisfactory preforms free from the said defect are nowproduced. The preform for the inner layer may be molded after havingtransferred the other preform for the outer layer into a further anddiscrete mold employed to mold the former preform.

The method of the present invention may also comprise the step offorming a through-hole that perpendicularly penetrates a bottom of theouter preform when molding same. Although the through-hole could be‘drilled’ in and through the bottom of the outer preform after havingmolded same, through-hole may more preferably be formed at the step ofmolding the outer preform, reducing the number of necessary steps.

Also in the method of the present invention, an outer preform may have athrough-hole formed in its bottom and penetrating it perpendicularlythereto. When an inner preform is formed inside the outer preform, aportion of the inner preform may be caused to protrude outwards throughthe hole. Thereafter, such a portion jutting from the inner layer bottomwill be collapsed to provide a flange disposed outside the outer layerbottom, by a stretching rod during the blow molding process. Thus, theinner layer will be prevented from departing from the outer layer bottomin a stretched laminated container.

The present invention is applicable to manufacture of the laminatedbottle comprising an inner layer laminated on an outer layer and havingone or more ventilation holes formed in the outer layer so as to allowambient air to flow in between the outer and inner layers. Such a methodmay consists of the step of injection molding a preform for the outerlayer, the subsequent step of injection molding an inner preform insidethe outer preform and the final step of blow molding a parisonconsisting of such outer and inner preforms. Those ventilation holes maybe formed while injection molding the outer preform, so that the innerpreform may be formed subsequently with pins inserted in the ventilationholes.

According to this method, the ventilation holes are formed when theouter preform is injection molded. Therefore, such a drawback in theprior art that the inner layer has been likely to be injured whenforming the ventilation holes in the outer layer during the blow-moldingstep, is now resolved herein. Any works for piercing such holes one byone in the injection molded outer layer are no longer necessary, thusenhancing manufacture efficiency.

Those outer and inner layers may have respective molded configurationseach composed of a body portion and a mouth portion to constitute abottle. To protect the mouth portions of the outer and inner layers fromseparation from each other, a relatively large thickness of the innerlayer may for instance be effective. The outer layer may be squeezableso as to readily deform itself elastically if depressed with a user'shand, or alternatively may be rigid in the event that a pump for suckingthe content of bottle would be attached to the mouth portion.

In the method of the present invention, the stratified parison maypreferably be blow molded in such a way that the stretching fororientation of the outer preform is effected below a portion where theventilation holes are located. The ventilation holes in this case areprotected well from deformation due to the step of stretching fororientation, lest should be closed with any amount of the resinsurrounding the holes. Stretching for orientation does not take placearound the ventilation holes, so that the inner layer portions presenttherearound may sustain the same wall thickness as that of un-stretchedpreform. However, the body of the inner layer for containing the content(liquid content) can however be made a thin film in shape and structure.At the same time, the inner layer portions around the holes may sothickened as to elastically restore well its natural configuration. Theinner layer constructed to naturally close the ventilation holes willhowever be depressed readily by external air pressure. It will deformitself inwardly so as to open those holes when ambient air is allowed toenter the interlayer space through them. The ventilation holes behave asif they were valves, so that it is no longer necessary to incorporateany extra or additional valve that would increase the number ofconstituent parts and raise manufacture cost.

In this method of the present invention described above, variousappropriate manners may be employed to make the ventilation holes solelyin the outer layer. For example, the outer preform may be injectionmolded using a cavity segment and a core segment, and then left in thecavity segment. The inner preform will subsequently be injection moldedusing the cavity segment in combination with another core segment, thelatter substituting for the first-mentioned core segment. Further, theventilation holes may be formed by causing pins to contact the firstcore segment before the resin becomes hard at the step of injectionmolding the outer preform. The ventilation holes are allowed to remainclosed with the pins while the inner preform is injection molded.

Such a method described above may be conducted using the followingapparatus. Namely, this apparatus will be used to produce a parison tobe blow molded into a delaminatable laminated container that is composedof an outer and inner preforms and has ventilation holes only in theouter layer at desired portions thereof A mold constituting thisapparatus may characteristically comprise a cavity segment and coresegments that can selectively be fastened to the cavity segment so as tomold the outer preform at first, and subsequently mold the innerpreform. Also characteristically, this apparatus further comprises oneor more pins in connection with the cavity segment in order to form theventilation hole(s). Those pins can shift themselves between theirprojected position contacting the first-mentioned core segment and theirretracted position embedded in the cavity segment.

Although the pins in the described example to form ventilation holes arelocated in connection with the cavity segment, they may alternatively bedisposed in a lip segment if the apparatus has same. In this case, thepins at their retracted position will be enclosed with said lip segment.

Further in an alternative method of forming ventilation holes only inthe outer preform, this preform is formed using an injection mold andthen removed therefrom. This outer preform will then be inserted in afurther injection mold for forming the inner preform so that pinsequipped in connection with the further mold are inserted from outsideinto rough ventilation holes that have been formed. Inner ends of thosepins will be brought into flush with the inner surface of the outerpreform, before the inner preform is injection molded.

Such a method described above may be conducted using the followingapparatus. Namely, this apparatus will be employed to produce a parisonto be blow molded into a delaminatable laminated container that iscomposed of an outer and inner preforms and has ventilation holes onlyin the outer layer at desired portions thereof This apparatus maycharacteristically comprise an injection mold for forming the outerpreform and a further injection mold for forming the inner preform. Pinsfor forming the ventilation holes are equipped in the first-mentionedmold so as to be shifted between their projected and retractedpositions. The secondly-mentioned mold comprises pin-shaped stoppersthat are to be inserted from outside into the ventilation holespreviously formed in the outer preform.

The method described above addresses parisons that are to be blow moldedto give the delaminatable types of laminated containers. However thepresent invention is not restricted thereto but is applicable to avariety of laminated articles (such as laminated parisons) that areinjection molded and each composed of two or more resin layers. In otherwords, the present invention proposes a method of making ventilationholes solely in an outer layer of an injection molded laminated producthaving an inner layer inside the outer layer. The methodcharacteristically comprises the steps of injection molding the outerlayer and then molding the inner layer so that the ventilation holes areformed during the step of injection molding the outer layer, wherein theinner layer is injected in such a state that pins are inserted in theventilation holes.

The parison-forming mold employed in the apparatus and method of thepresent invention may comprise at least one cavity segment and at leastone core segment. This mold may further comprise (a) projectablemember(s) that is(are) equipped in the cavity segment so as to contactthe side surface of the core segment. An appropriate means may also beincorporated to drive pins preferably serving as the projectablemembers.

When molding the outer preform in the described mold, this preform'sportions where the projectable members are temporarily located can notbe filled with a resin for forming this preform. As a result, thoseportions will define the ventilation holes penetrating that preform froman outer surface to inner surface thereof This means that theventilation holes as air passages can be formed already at the same timeas the outer preform is molded.

The projectable member incorporated in the mold described above may beheld in and by the lip segment so as to be capable of contacting thecore segment's side face. Alternatively, that member may be held in andby the core segment so as to contact with the inner surface of thecavity segment or the lip segment. In any case, the projectable membermay preferably be located below a threaded portion surrounding a mouthof the container that will be produced from the preform.

Also, this method of the present invention comprises the step of formingone or more ventilation holes that penetrate the outer preform from anouter surface to inner surface thereof, at the same time as this preformis molded. The ventilation holes are thus formed already at the step offorming the outer preform. The present method now eliminates the probleminherent in the prior art that has been injuring the inner layer whenforming the ventilation holes in the outer layer during the blow moldingstep. Further, works for piercing such holes one by one in the injectionmolded outer layer are no longer necessary, thus enhancing manufactureefficiency.

The delaminatable inner preform is formed herein onto the inner surfaceof the outer preform so that, preferably, their portions located belowthe ventilation holes are subsequently stretched for orientation.

According to this method, inner layer portions corresponding to theventilation holes maintain an original wall thickness, so that each ofsuch relatively thickened portions may function as a kind of valvecooperating with the ventilation hole. Thus, manufacture process becomessimpler and less expensive, as compared with the case of preparing extraand discrete valves.

Also in the present method, an inner end of the projectable member maybe located substantially in flash with the inner surface of the outerpreform when the inner preform is molded using the mold described above.

Due to this feature, a resin forming the inner preform may be preventedfrom flowing into portions that are intended to form the ventilationholes in the outer preform.

In this manufacturing method described above, the ventilation holes maypreferably be formed below a threaded portion of the outer preform.

An apparatus for manufacturing laminated containers each having adelaminatable inner layers may comprise a first injector assembly formolding an outer preform having one or more ventilation holes thatpierce the preform from an outer to inner surface thereof The apparatusfurther comprises a second injector assembly for molding an innerpreform disposed inside the outer preform and capable of beingdelaminated therefrom, together with a stretcher assembly for carryingout the stretching for orientation step for the preforms' portionslocated below the ventilation holes. Further, this apparatus may be suchthat those ventilation holes are formed in such portions of the outerlayer that are located below its threaded portion.

THE BEST MODES OF CARRYING OUT THE INVENTION

Now some preferred embodiments of the present invention will bedescribed referring to the accompanying drawings.

FIG. 1 shows a comb shaped product 22 comprising a laminated bottle 20having a delaminatable inner layer that has been manufactured by amethod of the present invention. The comb shaped product 22 is suitedfor uniformly applying a content such as a hair dye to hair. When a usergrips and presses the bottle 20 to be deformed, a liquid as the contentof the bottle will flow through a passage not shown but extendingthrough a comb shaped cap 21 and will exude forth out of several holesformed in end portions of the comb. If the user stops gripping andpressing the bottle 20, it recovers its normal configuration. Such acharacter of the bottle 20 is called “squeezability”.

As shown in FIG. 2, the bottle 20 has a threaded portion 20 a formedintegral with its periphery around the bottle's mouth. As shown in FIG.3, this threaded portion 20 a is fastened into a mating threaded portion21a formed in the comb shaped cap 21 to thereby secure it onto thebottle 20. An outer layer 20 b of the bottle 20 has ventilation holes 20d so as to allow ambient air to flow into a space between the outerlayer 20 b and an inner layer 20 c. Those ventilation holes 20 d mayappropriately be formed in an upper portion of the bottle's body or in abottom thereof. In the drawings, the ventilation holes are located belowthe threaded portion 20 a. In use of the bottle 20, its body will bedepressed by a user with his or her hand or by any other way, beforesubsequently releasing his or her hand therefrom. As a result, ambientair will flow through the ventilation holes 20 d in between the outerlayer 20 b and inner layer 20 c, so that the inner layer will remaindepressed and shrunk. The bottle body may be depressed later again whilepreventing ambient air from flowing into the interior of the innerlayer, and be shrunk to compress air between said layers to therebysqueeze the content of this bottle.

As shown in FIG. 3, the bottle 2 is composed of the outer layer 20 b andthe inner layer 20 c formed therein. The outer layer 20 b may be made ofa PET (viz., polyethylene terephthalate), an EVOH (viz., copolymer ofethylene and vinyl alcohol) or the like. The inner layer 20 c is a filmdelaminatable from the outer layer 20 b and capable of deformationrelative thereto. A material for forming the inner layer may be apolyolefin resin (such as a polyethylene) of an excellent gas-barrierproperty. The inner layer has a melting point and a temperature ofthermal deformation, both lower than those of the outer layer.

The ventilation holes 20 d penetrate not the inner layer 20 c but theouter layer 20 b from an outer surface to an inner surface thereof.These holes may not be closed with the comb shaped cap 21.

The cap 21 is formed integral with a valve 21 b facing the mouth of thebottle 20. This valve may readily open when the content inside the innerlayer 20 c moving into the cap 21, however, prevent the content frommoving back from the cap 21 into the interior of inner layer 20 c. Dueto this structure, ambient air is prevented flowing into the cap 21through holes formed in end portions of the comb.

When the user grips the laminated bottle 20 to cause deformation of theouter 20 b and inner layers 20 c, the content inside the inner layer 20c moves into the cap 21. If the user stops gripping and pressing thebottle 20, it recovers its normal figure. However, the inner layer 20 cmaintains its depressed configuration, and ambient air flows into aspace between the outer 20 b and inner layers 20 c through theventilation holes 20 d. If and when the user depresses the bottle 20again, these holes are closed with the inner layer 20 c by the user'sfingers so that the air between layers does not leak out of the bottle.Deformation of the outer layer 20 b consequently decreasing its capacitymay allow the air to press the inner layer 20 c, subsequently itscontent thereof will be squeezed out into the cap 21.

In FIG. 4, the content in the inner layer 20 c has partly been squeezedout. In detail, this figure shows a bottom portion of the inner layer 20c that has been delaminated from the outer layer 20 b due to such adecreased capacity thereof. However, the inner and outer layers are inengagement with each other at their central bottom portions lest theinner layer 20 c should come off the outer layer 20 b. Such anengagement 20 e is provided by the structure that the bottom portion ofthe inner layer 20 c fixedly fits in a through-hole 20 d, with this holehaving been formed in the bottom of the outer layer 20 b. In detail, theportion expands itself to assume a flange-like shape disposed in anouter bottom surface of the outer layer 20 b.

Next, FIGS. 5 to 11 illustrate molds that are designed to form parisonsand to blow mold same in order to produce laminated bottles. Also shownin these figures are a method of and an apparatus for making thelaminated bottles. The laminated bottle 20 in the present embodimentwill be produced by the injection-blow-molding method, wherein theinjected parisons are biaxially stretched while blow molding same. Arotary plate 19 is supported on a frame not shown and intermittentlydriven in one way. This plate 19 will cause a lip segment 2 to circulatebetween an injection station (namely, an injection molding apparatus), ablowing station (viz., a blow molding apparatus), and a dischargingstation, sequentially in this order. This lip segment consists of splithalves disengageable sideways from each other rightwards and leftwards.A driving means not shown will open or close the lip segment. Thissegment remaining closed will support the mouth of parison andsubsequently support the laminated bottle obtained by stretching theparison. The bottom surface of the rotary plate 19 holds the lip segmentin place.

At the injection station (viz., in the injection molding apparatus), theouter and inner preforms are molded. In this embodiment, the injectionstation is divided into a first injection station for molding the outerpreform (viz., an apparatus for injection molding the outer layer) and asecond injection station for molding the inner preform (viz., a furtherapparatus for molding the inner layer). In detail, the injection moldedouter preform will be removed at first by opening its mold. Then, thispreform will be taken out and inserted into a mold for forming the innerpreform, so that it is injection molded to provide the parison to beblow molded subsequently.

FIGS. 5 and 6 show the process of forming the outer preform 7A at thefirst injection station. In the drawings, an injection core segment 1A(viz., a male mold), the lip segment 2, and a cavity segment 3A (viz., afemale mold) are disposed up and down in this order. After fasteningthese segments to each other in this way, a molten resin is injectedfrom a nozzle 6A into the cavity through a hot runner 5A, a nozzle 4Athereof and a gate ‘GA’ to produce the outer preform 7A.

The injection core 1A (the core segment) has a bore 3 a for receiving astick-shaped member, with this bore formed longitudinally of the coreextending through a central region thereof. A stick-shaped pin 13 (viz.,a first pin) is slidably held in that bore 3 a, in such state that saidpin 13 is displaceable between a retracted position where the pin willbe retracted into the core segment 1A and a projected position where itwill protrude from this segment to enter and seal the gate ‘GA’. Afterthe cavity segment is filled with an amount of molten resin, the pin 13facing the gate ‘GA’ will be forced into the cavity segment so as toclose the outlet of the hot runner nozzle 4A.

A bottom portion that is temporarily occupied by the pin 13 can not befilled with the resin for forming the outer preform 7A. This portionwill define a through-hole 71 in the bottom of the outer preform 7A.This means that the through-hole can already be formed using the pin 13at the step of molding the preform 7A. The pin is capable of projectingand being retracted by means of a solenoid 14 in this embodiment. Thissolenoid will be actuated with an electric current so as to cause thepin 13 to project towards the cavity segment. By ceasing application ofelectric current to and through the solenoid, the rod-shaped member 13will be retracted out of the cavity segment. It is a matter of coursethat a spring for urging the pin towards its retracted position can becombined with a means for supplying a compressed air for forcing the pin13 to protrude. Alternatively, a compression spring may be used toalways urge the pin to protrude, in combination of the pin itself 13 sothat pressure of the resin being injected displaces this pin away fromthe nozzle. In this case, injection of the resin will subsequently beinterrupted to lower that pressure to thereby release the spring andclose the nozzle.

It may be possible to use pins (viz., second pins) carried by and in themold for the purpose of forming the ventilation holes 20 d in thedelaminatable bottle, when the outer preform 7A is injection molded. Inthis case, those holes are preferably formed in regions located near themouth, or more preferably in regions located adjacent to but below thethreaded portion, because those portions will not be stretched duringthe step of blow molding. Instead, various prior art techniques may beemployed to form such ventilation holes. The forming of ventilationholes 20 d in the outer layer may be conducted later at a subsequentdiscrete step or simultaneously with the step of injection molding theouter preform 7A. Desirably, those projectable-and-retractable secondpins 23 may be disposed in the cavity segment 3 of the injection moldfor the outer preform 7A as shown in FIG. 11.

The preform 7A in which the through-hole 71 has been formed will then bepulled out of the cavity mold 3A and transferred to a second injectionstation. Subsequently, that preform 7A will be inserted into anothermold for forming the inner preform.

FIG. 6 illustrates how to form the inner preform 7B at the secondinjection station. In this figure of the drawings, the injection core1B, the lip segment 2 and the cavity segment 3B are arranged up and downin this order. After having fastened these members to each other in thismanner, an amount of another molten resin will be injected through anozzle 6B. This resin is caused to advance through a hot runner 5B and anozzle 4B and into the cavity where the inner preform 7B is to beformed. The injection core 1B has a distal end that is for insertioninto the cavity, and this end has a diameter smaller than that of theother injection core's 1A similar distal end, by an extent correspondingto wall thickness of the preform 7B. The cavity segment 3B has a recess31 facing the through-hole 71 that has been formed in the perform 7A. Agate GB is formed on the bottom surface of the recess 31. Accordingly,the gate GB is spaced downwards and outwards from the through-hole 71and a flange 72 made of the resin forming the inner preform 7B isdisposed out of the through-hole 71 in the outer preform 7A. In theexample shown in the drawings, the flange 72 protrudes outwards from thethrough-hole 71, though another fashion of injection molding mayalternatively be employed so that the flange has its outer end surfacein flush with the outer surface of the outer preform 7A.

Both the through-hole 71 and the recess 31 will thus be filled with themolten resin forming the inner preform 7B. A portion of the amount ofmolten resin enters the through-hole 71 and bulges out on the outerbottom surface of the outer preform 7A. The mold for forming the innerpreform 7B may not necessarily be specially designed as to its gate‘GB’, but any ordinary pin gate (viz., direct gate) may be employed.

The mold having operated to form the inner preform 7B will then beopened, but allowing the lip segment 2 to continue to hold a parison 7consisting of the outer and inner preforms 7A and 7B.

At the blowing station shown in FIGS. 7 to 9, a blow core segment 9having a stretching rod 8 attached thereto, the lip segment 2 forholding the parison 7, a blow cavity segment 10, and a bottom segment 11are arranged up and down in this order. After fixing these segments toeach other and then placing the parison 7 in the blow cavity segment 10,the parison 7 will be heated. Subsequently, the stretching rod 8 isdriven to move downwards to insert its end portion in the parison 7.This rod will push a bottom of the cylindrical parison 7 downward toeffect the so-called ‘longitudinal stretching’. At the same time, therod transversely stretches the parison by allowing the air to flow intoit through the blow core segment 9 in order to ‘transverse stretching’,thereby biaxially orientating the resin molecules.

At a discharging station for taking out molded products as shown in FIG.10, an ejector rod 23, the lip segment 2 for holding a laminated bottle,and a transporting apparatus 24 like a conveyor belt are arranged up anddown in this order. The ejector rod has an ejecting foot 25 at itsdistal end. This foot 25 will be fitted in the mouth of bottle 20,before opening the lip segment 2 in a horizontal direction to lay thebottle on the conveyor.

As described above, the present invention is characterized in that theinner preform 7B having a lower thermal deformation temperature than themolding temperature of the outer preform 7A is molded therein aftermolding same. In the prior art, wherein a preform of an inner layer hasbeen molded at first, the inner preform has tended to thermally deformitself when subsequently molding the outer preform. This drawback isovercome herein, and satisfactory preforms free from the said defect arenow produced. In a case wherein the mold as shown in FIG. 5 is used toprepare the outer preform 7A, the latter will have the through-hole 71penetrating its bottom. Any drilling work that would otherwise benecessary can now be dispensed with to improve manufacture efficiency. Aportion of molten resin forming the inner preform 7B will flow throughthe hole 71 to form a bulge on the outer bottom surface of the outerpreform 7A, when the former preform is molded inside the latter havingthat hole. The stretching step conducted at the blow molding stationwill depress the bulge. This depressed bulge as a portion of an innerlayer 20 c constituting a stretched laminated bottle 20 will thusprovide a flange present on that outer bottom surface of an outer layer20 b. Due to this feature, the inner layer 20 c is inhibited fromdisengaging from the bottom of outer layer 20 b.

In the embodiment described above, the first injection station forpreparation of the outer preform 7A is distinct from the second one forthe inner preform 7B. However, only one and the same station may be usedto mold the latter preform 7B after molding the former 7A. In detail,the injection core 1A will be pulled out for subsequent insertion ofanother core for molding the inner layer. A resin passage for guidingthe molten resin for the inner layer 7B to be injected into the cavitysegment may be provided in and through the latter injection core.

The pin 13 disposed in the injection core 1A in the embodiment describedabove may alternatively be disposed in the cavity segment 3A. In a casewherein the pin is arranged not to face the outlet of molten resin, itcan be fixed in the injection core 1A or cavity segment 3A. The presentmethod in the described example is applied to manufacture of thelaminated container comprising the single outer layer and the singleinner layer. However, it may be used to manufacture the container ofanother type whose outer and/or inner layers are respectively composedof two or more layers or strata.

In the embodiment described above, the gate ‘GB’ of the mold forinjecting the inner layer is disposed in the cavity segment 3B. The gateGB may alternatively be located in the core segment 1B, and preferablybe arranged at the central end portion (distal end) thereof. Due to thisfeature, it is unnecessary to make the through-hole in the outer preform7A.

FIGS. 11 to 17 show further embodiments in which the inner preform ismolded at the same place by exchanging the injection core with anotherone after the outer preform has been molded. In this regard, it is to benoted that in the preceding embodiments the outer and inner preforms aremolded at discrete and respective injection stations. FIGS. 11 and 12illustrate the step of molding the outer preform 7A. In these figures,the injection core 1A, the lip segment 2, and the cavity segment 3 arearranged up and down in this order. After fastening the mold to engagethese segments with each other in a vertical direction, the molten resinis injected from a nozzle 6. The injected molten resin flows into thecavity through a hot runner 5 and a nozzle 4 thereof to prepare theouter preform 7A.

The cavity segment 3 comprises a couple of horizontally formed aperturesfor receiving two pins 3 a. The apertures 3 a hold respectiveprojectable members slidable therein, and those members may be secondpins 23. A distal end of each second pin 23 will protrude inwards tocontact the core segment when charging the molten resin (before or afterthe beginning of charge). These pins 23 form ventilation holes 20 d atthe step of molding the outer preform 7A. In this embodiment, solenoids24 will drive the pins 23 to be retracted and projected. For example,these solenoids each will be actuated with an electric current so as tocause each pin 23 to protrude towards the cavity segment and contact thecore segment 1A. By ceasing application of electric current to andthrough the solenoid, each pin 23 will be retracted away from the cavitysegment. It is a matter of course that a combination of a spring forurging the pin towards its retracted position with a means for supplyinga compressed air forcing the pins 23 to protrude may be employed.Alternatively, a distal end surface of each pin 23 may be recessedcorresponding to curvature of the injection core 1A.

FIG. 13 shows the manner of molding the inner preform 7B. The injectioncore 1A has been pulled out, and another core 1B is subsequentlyinserted as shown in this figure. The lip segment 2 and cavity segment 3are the same as those used to mold the outer preform. As for the pins23, they are shown at the same positions as those shown in FIGS. 11 and12. In other words, their distal ends are arranged to be substantiallyin flush with the inner surface of the outer preform 7A. The injectioncore's 1B end portion entering the cavity segment has a diameter smallerthan that of the core's 1A end, providing a difference between themcorresponding to the wall thickness of the inner preform 7B. Also, theinjection core 1B has a passage for guiding the molten resin into thecavity segment for molding the inner preform 7B (shown by dotted linesin the figure). As described above, the distal end of each pin 23 iskept generally in flush with the inner surface of the outer preform 7Awhile molding it, so that the molten resin of the inner preform 7B isprevented from flowing into the ventilation holes 20 d of the formerpreform.

After molding the inner preform 7B, the pin 23 will be retracted to openthe mold. Both the preforms 7A and 7B (a combination of 7A with 7B iscalled ‘parison 7’ hereafter) are however gripped with and held by thelip segment 2, even after opening the mold.

At the blow station shown in FIGS. 14 to 16, a blow core segment havinga stretching rod, the lip segment temporarily holding the parison 7, ablow cavity segment 10 and a bottom segment 11 are arranged up and downin this order. After engaging them with each other and putting theparison 7 into the blow cavity segment 10, the stretching rod 8 will bedriven to have its distal end inserted into the parison 7. This rod 8will subsequently stretch the parison in a longitudinal direction bypressing down the bottom thereof This parison 7 is simultaneouslystretched also in a transverse direction with a compressed air blownthrough the blow core segment 9 and into said parison. In this state,the region or portion (near the lower portion of the container's mouth)where the ventilation holes 20 d are located is firmly held in thesegments. Therefore, the stretching for orientation will not take placein the region adjacent to those ventilation holes. After completion ofthis stretching step for orientation, the laminated bottle will cooleddown to give a finished product.

At the discharging station shown in FIG. 17, an ejector rod 23, the lipsegment 2 holding the laminated bottle 20 and a transporting apparatus24 like a conveyor belt are arranged up and down in this order. Anejecting foot of the rod 25 will be fitted in the mouth of bottle 20,before opening the lip segment 2 sideways to lay the bottle on theconveyor 24.

As discussed above in detail, the ventilation holes 20 d are formed atthe step of molding the outer preform 7A. This method wherein thoseholes 20 d are produced when the outer preform is blow molded doestherefore eliminate any problem that the inner layer has been injured inthe prior art when forming the ventilation holes in the outer layerduring the blow molding step. Further, works for piercing such holes oneby one in the injection molded outer layer 20 b after completing thelaminated bottle 20 are no longer necessary, thus enhancing manufactureefficiency. After molding the delaminatable inner preform on the innersurface of the outer preform, the stretching for orientation of thepreforms is carried out only for a region thereof located below theventilation holes 20 d. Thus, the inner layer's portion located in aremainder region where the ventilation holes in the outer layer arepresent will keep its original or ‘non-stretched’ thickness. Such arelatively thicker portion may function as ‘valves’ cooperating withthose ventilation holes 20 d, so that manufacture process is nowrendered simpler and inexpensive as compared with the case of preparingdiscrete valves. In addition, the inner end of the pin 23 is positionedherein to be generally in flush with the inner surface of the outerpreform 7A during the molding of inner preform 7B. Due to this feature,the resin forming this preform 7B is prevented from filling spaces wherethe ventilation holes 20 d are to be formed in the outer preform 7A.

In the described embodiment, the inner preform 7B is molded at one andthe same station where the outer preform 7A has been molded, butnecessitating another injection core. Alternatively, such an injectionstation may be divided into a first and second injection stations sothat first station (i.e., first injection apparatus) operates to moldthe outer preform 7A. In this case, the second injection station (i.e.,second injection apparatus) will operate to mold the inner preform 7B.In detail, the outer preform 7A just molded will be removed from thefirst station's mold, and then transferred into the second station'smold so as to be laminated with the inner preform 7B. In this case,clogging pins capable of insertion into the ventilation holes of outerpreform may be employed and incorporated in the mold of the secondstation for injection molding the inner preform. The outer preform hasto be placed in the second mold in such a manner that its ventilationholes are exactly aligned with those pins, which are subsequentlyinserted from outside so as to have their inner ends generally in flushwith the inner surface of outer preform. The inner preform is laminatedon the inner surface of the outer preform.

In an also preferable example, the inner preform 7B has its upper endportion extending beyond the upper rim of outer preform 7A and bent downthere to reach the upper end of the threaded portion 20 a. In thisexample, the lip segment 2 will be replaced with another or extra lipsegment, after cooling down the outer preform 7A. Such an extra lipsegment will provide a clearance between it and the outer and upperregional surface of the outer layer's 7A threaded portion 20 a. Theresin forming the inner preform 7B will flow into this clearance toproduce such a bent-down top for this preform.

The pins 13 disposed in the cavity segment 3 in the embodiment describedabove may be replaced with another pair of pins 23 contacting the sidesof injection core 1A. Alternatively, these pins 23 may be equipped inthe injection core 1A in such a way as to be in contact with the innersurface of the cavity segment 3 or lip segment 2. Since the lip segment2 can be split into halves in a transverse direction, appropriateprotrusions fixed in and extending in this direction will contact thecore segment IA when it takes a fastened position. In the example shownin FIG. 13, the molten resin forming the inner preform 7B is injectedthrough a passage formed in the injection core 1B. However, this resinmay alternatively be injected from a through-hole opened in the bottomof the outer preform 7A. The present method applied to the laminatedcontainer comprising the single outer and inner layers in the describedembodiments and examples, can also be used to manufacture any other typecontainer whose outer and/or inner layers are composed each of two ormore layers or strata.

The injection mold core segment for molding the inner preform 7B mayhave at its outer periphery a plurality of vertical grooves (extendingup and down). In this case, several thickened wall portions 30 will beproduced on the preform to respectively extend up and down at angularintervals as shown in FIGS. 18 and 19. Although the number of thoserib-shaped thick portions 30 is ‘four’ in the illustrated example, itmay be ‘two’, ‘three’, ‘five’ or more. A parison of this configurationwill be blow molded to give a finished product that has an inner layer20 c comprising vertical thick portions arranged at angular intervals.If a simply flat inner layer 20 c lacking in such thickened portions isdepressed to assume a shrunk appearance in use, then its middle regionor upper end region would be highly likely to be depressed at first tochoke the bottle to thereby hinder subsequent discharge of the content.However in the case just mentioned above, it is sure that the contentwill be exhausted thoroughly and smoothly.

In another example shown in FIGS. 20 and 21, a helical rib-shapedthickened portion 31 is formed on and integral with the body of innerlayer 7B. This layer of a finished bottle obtained by blow molding theparison 7 will shrink itself uniformly, lest any intermediate transversezone perpendicular to its longitudinal axis should be depressedcompletely and pre-ceding remainders to thereby choke the bottle

According to the present invention, a through-hole is formed in a bottomof a preform, at the step of preparing same to provide an outer layer inthe finished product. The number of manufacture steps is now reduced, ascompared with the case of using a drill to form the hole, thus loweringmanufacture cost of laminated containers.

In the invention, the inner preform having a lower thermal deformationtemperature than the molding temperature of the outer preform is moldedtherein after having molded same. One of drawbacks inherent in the priorart molding the preform of an inner layer at first resides in that theinner preform is thermally deformed while molding the preform of anouter layer This problem is now resolved to provide qualified preformseach composed of a plurality of layers.

When molding the inner preform inside the outer preform having thethrough-hole longitudinally formed at the bottom thereof, a resin forthe inner layer is caused to flow through and out of the hole. Aflange-shaped member is provided herein as a bottom portion of the innerlayer constituting the stretched laminated container. Such a flangeformed outside the bottom of the outer layer will prevent the innerlayer from curling up during use of the product.

Also in the present invention, the inner layer may be formed integralwith a plurality of thickened portions extending up and down at angularintervals, or thick portions extending in a helical direction. Thesestructures may restrict shrinkage of the inner layer in such a way thatthe upper end region thereof would otherwise be depressed at first tochoke the bottle. The content of the container provided herein and freefrom such a problem will now be exhausted thoroughly and smoothly.

Further, since ventilation holes are formed at the step of molding theouter preform, an operation for forming these holes only in the outerlayer is readily and surely conducted without injuring the inner layerof the laminated delaminatable container. Thus, an improvement isachieved not only in respect of the yield of products but also as to themanufacture efficiency in production of such delaminatable laminatedcontainers each having ventilation holes.

After having molded the delaminatable inner preform on the inner surfaceof the outer preform, the stretching for orientation thereof isconducted for the portion thereof located below the ventilation holes.Thus, the inner layer portions corresponding to regions where theventilation holes have been formed in the outer layer will keep itsoriginal or ‘un-stretched’ wall even after the stretching of theselayers. Such a relatively thick portion may function as a valvecooperating with each corresponding ventilation hole, consequentlyrendering simpler the manufacture process and lowering manufacture costas compared with the case of molding extra or discrete valves.

When molding the inner preform, the inner end of the pin employed hereinis located to be substantially in flush with the inner surface of theouter preform. Thus, the resin forming the inner preform can beprevented from flowing into portions intended to form the ventilationholes in the outer preform.

What is claimed is:
 1. A method of making a laminated bottle having anouter layer and an inner layer laminated on an inner surface of theouter layer so as to be capable of delaminating from the surface, themethod comprising the steps of: injection molding an outer preform forthe outer layer by injecting a molten first resin, and forming athrough-hole in the outer preform being injection molded at a portionthereof facing an injection gate for injecting the second resin, whereinthe through-hole is formed by a first pin, the pin projecting toward afurther injection gate for injecting the first resin through it afterinjecting of the first resin has been finished so that an end portion ofthe pin strikes the further gate; then injection molding inside theouter preform an inner preform for the inner layer by injecting a moltensecond resin through the gate and also the though-hole to flow along aninner surface of the outer preform so that the preforms comprise aparison; and and finally blow molding the laminated bottle by blowingthe parison, wherein the second resin has a melting point lower thanthat of the first resin.
 2. A method of making a laminated bottle havingan outer layer and an inner layer laminated on an inner surface of theouter layer so as to be capable of delaminating from the surface, themethod comprising the steps of: injection molding an outer preform forthe outer layer by injecting a molten first resin, and forming athrough-hole in the outer preform being injection molded at a portionthereof facing an injection sate for injecting the second resin; theninjection molding inside the outer preform an inner preform for theinner layer by injecting a molten second resin through the gate and alsothe though-hole to flow along an inner surface of the outer preform sothat the preforms comprise a parison; and finally blow molding thelaminated bottle by blowing the parison, wherein the second resin has amelting point lower than that of the first resin, the inner preform isinjection molded so that a bulge of the second resin is formed, thebulge projecting outwardly through the through-hole from the outerpreform, and a stretching rod used to stretch the parison longitudinallydepresses and collapses the bulge at said blow molding.
 3. A method ofmaking a laminated bottle having an outer layer and an inner layerlaminated on an inner surface of the outer layer so as to be capable ofdelaminating from the surface, the method applied to make the laminatedbottle having at least one ventilation hole to allow ambient air to flowin between the outer and inner layers, and comprising the steps of:injection molding an outer preform for the outer layer by injecting amolten first resin; then injection molding inside the outer preform aninner preform for the inner layer by injecting a molten second resin sothat the preforms comprise a parison; and finally blow molding thelaminated bottle by blowing the parison, wherein the second resin has amelting point lower than that of the first resin, the ventilation holeis formed at the step of injection molding of the outer preform, andwhen the inner preform is subsequently injection molded, a second pinhas been inserted from outside and through the outer preform in such amanner that an end portion of the second pin is held substantially inflush with the inner surface of the outer preform.
 4. The method asdefined in claim 3, wherein a cavity segment and a first core segmentfor molding the outer preform are used for injection molding the outerpreform, the method further comprising the additional step of replacingthe first core segment with a second core segment for molding the innerpreform, without removing the outer preform out of the cavity segment,with the additional step being interposed between the steps of injectionmolding the outer and inner preforms, wherein the cavity segment and thesecond segment are used for injection molding the inner preform, formingthe ventilation hole comprises striking the second pin against the firstcore segment before the resin of the outer preform cures at the step ofinjection molding the outer preform, and the ventilation hole remainsclosed with the second pin during injection molding the inner layer. 5.The method as defined in claim 4, wherein the second pin is capable ofshifting between its projected position where the pin strikes the firstcore segment clamped to the cavity segment and its retracted positionwhere the pin is embedded in the cavity segment.
 6. The method asdefined in claim 4, wherein the outer preform is held by a lip mold allthrough the first, second and third steps, and the second pin is capableof shifting between its projected position where the pin strikes thefirst core segment clamped to the cavity segment and its retractedposition where the pin is embedded in the lip mold, and the pin at theprojected position clogs the ventilation hole but the pin at theretracted position leaves the hole opened.
 7. The method as defined inclaim 3, wherein a first injection mold is used for injection moldingthe outer preform and a second injection mold is used for injectionmolding the inner preform, and the method comprises the steps, betweenthe steps of respectively injection molding the outer and innerpreforms, of releasing the outer preform from the first mold, loadingthe released outer preform into the second mold, inserting the pin intothe ventilation hole that has been formed in the outer preform, andwherein the pin remains left is the ventilation hole during injectionmolding of the inner layer.
 8. The method as defined in claim 3, whereinthe parison is blow molded such that stretching for orientation of thepreforms is conducted for the portion thereof located below theventilation hole.